When switching over from the normal operation to the overrun fuel cut-off operation, there is inevitably a torque jump which can cause an irregular running of the Otto engine or an unwanted judder of the vehicle. The advantages which per se derive from the overrun fuel cut-off, such as a reduction in the fuel consumption, improved braking effect of the engine and lower noise emissions, for example, must be obtained at the expense of a degradation in driving comfort. The same problem arises when, after the overrun fuel cut-off operation, the normal driving operation of the vehicle must be resumed and the Otto engine must again generate a desired torque and deliver it to the vehicle.
Various measures have already been proposed for reducing this undesirable or acceptable torque jump which is caused by the cut-off of the fuel injection in the overrun operation. The transition was not controlled in older engines, for example, i.e. the fuel injection was simply stopped in the overrun fuel cut-off operation.
A known and relatively effective measure for counteracting the torque jump during the transition to the overrun fuel cut-off is to adjust the ignition angle significantly in the direction of ignition retard, such that the combustion of the fuel-air mixture in the cylinder of the Otto engine is still reliably guaranteed. In this case, the fuel continues to be injected during the intake phase until the switchover into the overrun operation. This results in a reduced torque, since the fuel-air mixture can no longer develop its full power in the retarded ignition phase. In many cases, however, this reduction is not sufficient to achieve a gentle transition to the overrun fuel cut-off.